Oxide Semiconductor Transistor Memory Cell for Low Power Data Retention
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Solution Overview
Problem
Semiconductor devices using oxide semiconductors face challenges in achieving low off-state current, low power consumption, high reliability, and the ability to store multi-bit data with high retention characteristics without the need for a verify operation.
Innovation Solution
A semiconductor device comprising a first transistor, a second transistor, and a capacitor, where the channel region of the first transistor is formed with an oxide semiconductor film, and specific voltage applications are used for writing and reading data, allowing for high reliability and low power consumption without a verify operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a transistor using oxide semiconductor film is used, then off-state leakage current is reduced, but power consumption and data retention characteristics need further improvement
Solution Approach 1:
The invention divides the memory cell into two transistors (first transistor with oxide semiconductor film and second transistor) and a capacitor, where each component has a specialized function. The first transistor handles data writing with low off-state current, while the second transistor manages data reading, and the capacitor stores the data state, collectively achieving low power consumption and high reliability
Solution Approach 2:
The invention uses a composite structure combining oxide semiconductor film (for low off-state current characteristics) with conventional semiconductor materials (for high mobility and fast switching), creating a hybrid transistor system that leverages the advantages of both material types to achieve both low power consumption and high reliability
2Quantity of substance
If conventional memory structures are used, then multi-bit data storage is possible, but verify operation is required which increases complexity
Solution Approach 1:
The oxide semiconductor film transistor inherently maintains stable voltage levels due to its extremely low off-state leakage current, allowing the memory cell to self-maintain data states without requiring external verify operations. The device structure itself provides the stability needed for reliable multi-bit data storage
Solution Approach 2:
The invention pre-charges the bit line to a specific voltage level before data writing operations. This preliminary action, combined with the oxide semiconductor's stable characteristics, ensures that data states are reliably established and maintained without needing subsequent verify operations to confirm correct storage
3Reliability
If oxide semiconductor film is used for channel formation, then transparency and reliability are improved, but manufacturing precision requirements increase
Solution Approach 1:
The invention employs sputtering methodology with carefully controlled parameters (power, pressure, temperature, gas flow ratios) to deposit oxide semiconductor films with consistent thickness and composition. By optimizing these deposition parameters, the manufacturing process achieves high film quality and reliability while maintaining feasibility for mass production
Data Source
AI summary
To provide a semiconductor device which can write and read a desired potential. The semiconductor device includes a first transistor (Tr), a second Tr, and a capacitor. In the semiconductor device, operation of writing data is performed by a first step and a second step. In the first step, a low voltage is applied to a bit line and a first wiring to turn on the first Tr and the second Tr. In the second step, a first voltage is applied to the first wiring, and application of the low voltage to the bit line is stopped. Operation of reading the data is performed by a third step and a fourth step. In the third step, a high voltage is applied to the first wiring. In the fourth step, application of the high voltage to the first wiring is stopped, and a low voltage is applied to a capacitor line.